1. Field of Invention
The present invention relates to a recording device that has a thermal head, to a control method for a recording device, and to a control program, and relates more particularly to technology that prevents media transportation problems resulting from the thermal head and the recording medium sticking together.
2. Description of Related Art
Thermal printers (also called direct thermal printers) that record images of text and other content on thermal paper are known from the literature as one type of recording device for recording images on a recording medium. If a thermal printer of this type is left with the thermal paper held pressed between the thermal head and platen roller in the standby mode, the thermal paper can become stuck to the platen roller or the thermal head if the standby mode lasts for long or if the standby mode is short but the printer is used in a demanding high or low temperature environment.
To avoid this, Japanese Unexamined Patent Appl. Pub. JP-A-H11-320989 teaches turning the platen roller forward, reverse, and then forward when the standby mode lasts for a specified period of time in order to prevent the thermal paper from sticking completely. More specifically, JP-A-H11-320989 describes preventing adhesion by rotating the platen roller before the thermal paper and thermal head stick together as a result of pressure bonding between the thermal paper and thermal head caused by applying pressure therebetween for an extended time, fusion in a high temperature environment, or freezing in a low temperature environment.
Linerless label paper eliminates the liner that is commonly used to carry adhesive labels and becomes waste after the labels are removed, and thermal printers for recording on linerless label roll paper, which is linerless label paper wound into a roll, are conceivable.
Linerless label roll paper is coated with a release coating on the label side and with adhesive on the back side, and is wound into a roll with the adhesive side against the release coating layer. As a result, if the label paper is conveyed passed the thermal head with adhesive remaining on the release coating layer, the linerless label roll paper will quickly stick to the thermal head. The paper thus sticking to the thermal head can lead to paper transportation problems, resulting in the feed pitch being disrupted when paper feeding starts at the start of printing and other paper transportation errors.
If the method taught in JP-A-H11-320989 is applied to prevent such sticking, the platen roller must be frequently driven rotationally to prevent sticking because JP-A-H11-320989 is not intended for use with recording paper that has a sticky surface layer. As a result, operation becomes complicated or the interval between operations becomes too long and the paper cannot be separated.
The problem of the paper quickly sticking to the surface of the thermal head is not limited to linerless label paper, and may also occur when an overcoating has been applied to protect the surface.